22 MORPHOLOGY 



As soon as the spores are ripe they are capable of germination, and in 

 a dried state remain so for many years. This property is not peculiar to the 

 spores of bacteria : well-dried wheat germinates after being kept for twenty 

 years, and the spores of the smut-fungus may lie in a herbarium for eight 

 years and not lose their vitality (see Chap. VIII). Moistening with pure 

 water is not sufficient to cause germination of bacterial spores. A solution 

 capable of setting up a nutritive stimulus is necessary, and, of course, 

 a suitable temperature. 



The first stage of germination is the slow swelling up of the spore, 

 which gradually becomes less and less refractive (Fig. n, g a, h a, * 3). 

 In B. subtilis this phase lasts from one to three hours. Then the spore- 

 membrane bursts open at one point, and the contents, surrounded by 

 a delicate cell-wall, are protruded, and elongating soon assume the form 

 of a rod, the new bacillus (Fig. \x,h 2-6). The end of this often bears 

 for a long time the ragged remnants of the spore-membrane. Germination 

 is now complete, the whole process having taken about four or five hours. 

 One peculiarity connected therewith is worthy of remark. The spores of 

 B. subtilis are in shape short ellipsoids, having the longer axis parallel 

 to the longer axis of the cell that gave them birth. The new rod, on 

 germination, bursts through the side of the spore, and stretches itself at 

 right angles to the latter (Fig. 11, A 5), so that the longer axis of the new 

 generation crosses that of the old. The spores of B. anthracis and of 

 Clostridium butyricum, on the other hand, burst open at the end, so that the 

 axes of the new and old generation are continuous. Both these types of 

 germination are common among bacteria, but they are constant for the 

 same species, and therefore can be used for purposes of classification. 



The simplest germinative process is that shown by some harmless 

 saprophytic bacteria (e. g. B. leptosporus), where the spore itself grows 

 out without casting its membrane into the new bacillus (Fig. 11, i). In 

 this case the unchanged spore-membrane becomes the cell-wall of the young 

 rod, whereas in B. anthracis, B. subtilis, and Clostridium butyricum the 

 coat of the spore splits into two layers — an outer, which is "left as the 

 empty membrane, and an inner, which ensheathes the protruding contents 

 of the spore and becomes the cell-wall of the new-born bacterium. The 

 spores of many fungi also germinate in this way. 



De Bary (13) has described, under the name of arthrospores, structures 

 which have given rise to a great deal of misunderstanding. He gave this 

 name to certain cells in filamentous bacteria, such as Cladothrix (Fig. ia), 

 Thiothrix, &c, which detach themselves from their fellows and swim about 

 after the manner of swarm-spores, finally growing out into filaments again. 

 They are certainly reproductive cells (Gonidia), and may perhaps be termed 

 spores, in so far as a spore is subservient to reproduction. De Bary called 

 them arthrospores because they are formed from one joint or cell in the 



